1. Field of the Invention
The present invention relates to a polishing method and apparatus, and more particularly to such a method and apparatus for polishing a workpiece such as a semiconductor wafer. Further particularly, the present invention relates to such a method and apparatus wherein a workpiece to be polished and washed, particularly a dry workpiece, is loaded into the apparatus, is polished and then washed and dried therein, and wherein the resultant clean and dry polished workpiece is transferred from the apparatus. When a dry workpiece to be polished is loaded into the apparatus and a clean and dry polished workpiece is transferred from the apparatus, the method is referred to hereinafter as a xe2x80x9cdry-in, dry-outxe2x80x9d method. Still further particularly, the present invention relates to such a xe2x80x9cdry-in, dry-outxe2x80x9d method and apparatus including a plurality of operating units disposed in an array or cluster around at least one center robot having at least one robot arm, and having a transfer structure including separate and discrete transfer mechanisms including at least one first transfer mechanism for transferring a dry workpiece into the apparatus and for transferring the clean and dry polished workpiece from the apparatus, and at least one second transfer mechanism for transferring the workpiece between polishing and washing units of the apparatus.
2. Description of Related Art
Recent rapid progress in semiconductor device integration demands smaller and smaller wiring patterns or interconnections and also narrower spaces between interconnections which connect active areas. One of the processes available for forming such interconnections is photolithography. Although a photolithographic process can form interconnections that are at most 0.5 xcexcm wide, such process requires that surfaces on which pattern images are to be focused by a stepper be as flat as possible because the depth of focus of the optical system is relatively small.
It is therefore necessary to make the surfaces of semiconductor wafers flat to enable use of photolithography. One customary way of flattening the surfaces of semiconductor wafers is to polish them with a polishing apparatus.
Conventionally, such a polishing apparatus has a single function of polishing a semiconductor wafer. Therefore, in the case of washing a semiconductor wafer after polishing, the semiconductor wafer must be transferred or transported from the polishing apparatus to a washing apparatus. Further, in the case of polishing a semiconductor wafer again under different conditions after a first polishing operation, the semiconductor wafer must be transferred or transported from one polishing apparatus to another polishing apparatus. In such cases, the semiconductor wafers are manually transferred or transported by a movable container in which they are immersed in water to keep them from drying during transportation. However, since various apparatuses including a polishing apparatus and a washing apparatus are independently installed and the semiconductor wafers are transferred or transported by the movable container containing water therein, it is difficult to install the polishing apparatus, the washing apparatus and the like in a clean room of a semiconductor manufacturing plant and to automate completely various processes including a polishing process and a washing process.
In order to solve the above problems, there has been proposed an apparatus which has a polishing unit and a washing unit provided in a common housing. Further, if necessary, a plurality of polishing units can be provided in a common housing. In a polishing apparatus which has a polishing unit and a washing unit, or a plurality of polishing units in a common housing, it is conceivable to construct a cluster type of polishing apparatus which integrates a plurality of units including a polishing unit and a washing unit, as employed in a semiconductor manufacturing process such as etching or chemical vapor deposition (CVD).
However, in the case of constructing a cluster type of polishing apparatus which integrates a plurality of units and incorporates a universal transfer robot at a central position of the units, it is necessary to handle both a dirty and wet semiconductor wafer soiled with abrasive slurry or particles generated by the polishing operation and a clean and dry semiconductor wafer which is placed on a loading unit or an unloading unit. Therefore, a conventional robot incorporated in a cluster type of a semiconductor manufacturing processing apparatus cannot be used in a cluster type of polishing apparatus because such robot is not capable of handling separately both a clean semiconductor wafer and a dirty semiconductor wafer. If such conventional robot is incorporated into the polishing apparatus, a washing process and a drying process of the robot or a robot arm additionally are required, thus lowering throughput efficiency of the apparatus. Further, when such robot or the robot arm is left for a long time as it is, abrasive material or particles generated by the polishing operation adhere to the robot or the robot arm, resulting in contamination of subsequent semiconductor wafers or respective units of the polishing apparatus.
Therefore, it is an object of the present invention to provide an improved polishing method and apparatus wherein it is possible to achieve polishing of a workpiece and then to achieve washing and drying of the workpiece.
It is a further object of the present invention to provide such a method and apparatus wherein workpieces to be polished that are introduced to the apparatus are dry and wherein polished and cleaned workpieces that are discharged from the apparatus also are dry, wherein the method and apparatus operate according to a dry-in, dry-out principle.
It is a yet further object of the present invention to provide such a method and apparatus wherein it is possible to overcome the above discussed and other prior art disadvantages and to provide a much greater degree of manufacturing flexibility than has been possible in the prior art.
It is an even still further object of the present invention to provide such a polishing method and apparatus employing a cluster type arrangement of a plurality of units that perform various operations, as well as a transfer structure including exclusive means for handling a clean semiconductor wafer and exclusive means for handling a dirty semiconductor wafer. Thus, a transfer mechanism or mechanisms that handle a dry semiconductor wafer to be loaded into the apparatus and that handle a clean and dry semiconductor wafer that has been polished and then washed and dried and that is discharged from the apparatus are exclusive, discrete and separate from a transfer mechanism or mechanisms that transfer semiconductor wafers among polishing and washing systems of the apparatus. Thus, dry semiconductor wafers are loaded into the apparatus, and dry semiconductor wafers that have been polished and washed are transferred from the apparatus.
In accordance with one aspect of the present invention, there is provided a method and apparatus wherein a workpiece to be polished is transferred from a loading unit to a polishing system, whereat the workpiece is polished to form a polished workpiece. The polished workpiece is transferred from the polishing unit to a washing unit defining washing and drying systems. The workpiece is washed and then dried at the washing unit to form a clean and dry polished workpiece. The thus clean and dry polished workpiece then is transferred from the washing unit to an unloading unit. In accordance with a further feature of the present invention, the workpiece to be polished is transferred in a dry condition from the loading unit to the polishing unit.
According to another aspect of the present invention, there is provided a polishing method and apparatus for polishing a surface of a workpiece and washing the workpiece which has been polished. A universal transfer robot has at least one arm for transferring the workpiece. A plurality of units are disposed around the universal transfer robot and include a loading unit for receiving thereon the dry workpiece to be polished, a polishing system including at least one polishing unit for polishing the workpiece which is transferred from the loading unit, a washing system and a drying system defined by at least one washing unit for washing and drying the workpiece which has been polished and an unloading unit for receiving thereon the resultant washed and dried polished workpiece. A transfer structure includes an exclusive transfer mechanism that transfers a clean workpiece and another exclusive transfer mechanism that transfers a dirty workpiece. The loading unit, the unloading unit, the polishing unit and the washing unit are disposed around the universal transfer robot. A workpiece, i.e. a dry workpiece, is picked up from the loading unit by the universal transfer robot, transferred to the polishing unit, and polished by the polishing unit. After the polishing operation, the thus dirty workpiece is transferred from the polishing unit to the washing unit by another exclusive transfer mechanism and is washed and dried by the washing unit. After such washing and drying operations, the resultant clean and dry polished workpiece is transferred from the washing unit to the unloading unit by the universal transfer robot.
According to a further aspect of the present invention, the universal transfer robot has an arm for exclusively handling a clean workpiece and an arm for exclusively handling a dirty workpiece. The loading unit, the unloading unit, the polishing unit and the washing unit are disposed around the universal transfer robot. A workpiece, e.g. a dry workpiece, is picked up from the loading unit by the arm for exclusively handling a clean workpiece of the universal transfer robot, transferred to the polishing unit, and polished by the polishing unit. After such polishing operation, the thus dirty workpiece is transferred from the polishing unit to the washing unit by the arm for exclusively handling a dirty workpiece of the universal transfer robot, and is washed and dried by the washing unit. After such washing and drying operations, the resultant clean and dry polished workpiece is transferred from the washing unit to the unloading unit by the arm for exclusively handling a clean workpiece of the universal transfer robot
According to a still further aspect of the present invention, the transfer structure includes two universal transfer robots each having at least one arm for transferring the workpiece, and the plurality of units are disposed around the two universal transfer robots. One of the universal transfer robots transfers a clean workpiece and the other of the universal transfer robots transfers a dirty workpiece. The loading unit, the unloading unit, the polishing unit and the washing unit are disposed around the two universal transfer robots. A workpiece, e.g. a dry workpiece, is picked up from the loading unit by the universal transfer robot for exclusively handling a clean workpiece, transferred to the polishing unit, and polished by the polishing unit. After such polishing operation, the thus dirty workpiece is transferred from the polishing unit to the washing unit by the universal transfer robot for exclusively handling a dirty workpiece, and is washed and dried by the washing unit. After such washing and drying operations, the resultant clean and dry polished clean workpiece is transferred from the washing unit to the unloading unit by the universal transfer robot for exclusively handling a clean workpiece.